This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This proposal is part of a research program that aims to clarify (1) hemispheric specialization and independence, (2) interhemispheric interaction, and (3) interhemispheric control. These mechanisms of interhemispheric relations address three central theoretical concepts in cognitive neuroscience: modularity of processing, intermodular communication, and control of parallel modular processes. A core set of progressively complex lateralized behavioral paradigms developed in our laboratory have been designed to (1) explore individual differences in hemispheric specialization in attention, perception and language;(2) contrast different degrees of hemispheric independence, including independence strategies, resources and priming, and (3) analyze the control of parallel processing in the two hemispheres. These experiments range from sensorimotor integration in simple reaction time through phonetic perception and letter identification to complex word recognition. Each experimental paradi gm includes an intrahemispheric component for studying hemispheric independence, and an interhemispheric component for studying interhemispheric interaction and control. These experiments have been administered to normal subjects and to patients with complete cerebral commissurotomy, agenesis of the corpus callosum and patients with partial callosotomy both pre- and post surgically as well as with patients with selected lateralized lesions to examine the role of the right hemisphere in natural language processing. This proposal focuses on the study of the anatomical correlates with some of the same above mentioned behavioral measures of interhemispheric relations. With this approach we combine sophisticated cognitive theory and methodology on the one hand, with in-depth neuroscientific analysis that incorporates anatomical, physiological and clinical behavioral techniques, data and theory on the other. Thus, we use converging studies of normal subjects and parallel measures of brain structure (MRI), brain function, and behavior.